Here's a list of software that's essential for your testing and benchmarking of your computer's performance. By running these software, you are able to determine a system's capability, overall stability and compare it to other systems (benchmarking). All software featured below are freeware and are often used to test new computers as well as overclocked systems.
1. CPU Z
While not exactly a testing software, CPU-Z is a freeware that gathers information on some of the main devices of your system. It is really useful as it displays all information about your system such as processor type and specification, L1 and L2 cache size, motherboard and bios version, and RAM information. Good for identifying information that is critical for troubleshooting a problematic system.
Download CPU-Z 1.38 from cpuid.com
MemTest is a RAM reliability tester. By running MemTest you can ensure that your computer's RAM is functioning correctly. This is a good thing to check whenever you buy a new computer, install new RAM, or change the configuration of your machine (for instance, to overclock it). If you are the sort of user who likes to push the performance of your machine to the edge, relying upon whether your machine will boot after your new BIOS tweaks is a poor way to determine the safety of your new settings, you can use MemTest as a true test of stability.
Download Memtest from hcidesign.com
3. Disk Speed
This nifty piece of software performs disk speed test and provided details about how fast your disks can transfer data. The information provided includes data transfer rate for linear reads, random read transfer rate and the seek time of the drive.
Download Roadkil's Disk Speed from roadkil.net
This is a popular software among overclockers worldwide for benchmarking of their systems and is also a distributed computing project. The software is widely used for "torture tests". Testers often leave the system to run Prime95 for weeks and months on end. Prime95 uses the computer to find Mersenne prime numbers, and in the process of doing this, it pushes the CPU's floating point units extremely hard, causing the CPU to become extremely hot - making Prime95 an extremely viable software for testing system stabilty. There is also a Linux version called MPrime.
Download Prime95 from mersenne.org
If your computer passes all these tests, then you can be pretty confident that your computer is fit and ready to go!